Building Computer Vision Projects with OpenCV 4 and C++

Estimated pose calculation

From these 2D–3D correspondences, we can calculate 3D pose (rotation and translation) of the head, with respect to the camera, by way of the Point-n-Perspective (PnP) algorithm. The details of the algorithm and object pose detection are beyond the scope of this chapter; however, we can quickly rationalize why just a handful of 2D–3D point correspondences are suffice to achieve this. The camera that took the preceding picture has a rigid transformation, meaning it has moved a certain distance from the object, as well as rotated somewhat, with respect to it. In very broad terms, we can then write the relationship between points on the image (near the camera) and the object as follows:

This is an equation where